CHEYENNE, Wyo. (AP) — Laramie County investigators and federal agents are tracing the origin of a gun used in the accidental shooting of an 8-year-old boy in Cheyenne.

Two 8-year-old boys found the .25 caliber gun while building a fort in a field on April 7. Sheriff's department spokesman Gerry Luce told the Wyoming Tribune Eagle that one boy pulled the trigger and the bullet hit Gage McClellan in the chest. He was dead when deputies arrived.

Sheriff's investigators are working with agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives to figure out how the gun ended up in the field.